Figure 8.2. Schematic representation of the pathway of and resistances (rbl - boundary layer resistance; rsr - surface resistance; rias - intercellular air space resistance; rcw - cell wall resistance; rp - plasmalemma resistance; rc - cytosol resistance; ro - organelle resistance; rtotal - total resistance) encountered by gases diffusing into or out of plant tissues. As with Ohm's Law governing the flow of electricity (resistance = voltage/current), resistances in series can be added to give the total resistance.